Many reagents catalyzed by palladium or other transition metals require phosphine ligands (I. Ojima (publisher), Catalytic Asymmetric Synthesis, VCH, NewYork, Weinheim 1993; E. Negishi (publisher), Handbook of Organopalladium Chemistry for Organic Synthesis, Wiley-Interscience, New York 2002; M. Beller, C. Bolm (publisher), Transition Metals for Organic Synthesis, Wiley-VCH, Weinheim 1998; N. J. Whitcombe, K. K. Hii, S. E. Gibson, Tetrahedron 2001, 57, 7449-7476; D. Prim, J.-M. Campagne, D. Joseph, B. Andrioletti, Tetrahedron 2002, 58, 2041-2075; A. F. Littke, G. C. Fu, Angew. Chem. 2002, 114, 4350-4386). These often have the disadvantage, especially with regard to trialkylphosphines, to oxidize very easily in air, thereby becoming useless, or even pyrophoric (K. Sasse (publisher), Houben-Weyl, Methods of Organic Chemistry, 4th Edition, Volume XII/1, p. 69, Georg-Thieme-Verlag, Stuttgart 1963).
The problem with the oxidation sensitivity of phosphines can be bypassed by producing tetrafluoroborate salts from them, and they can be used as ligand precursors for catalysis reactions (M. R. Netherton, G. C. Fu, Org. Lett. 2001, 3, 4295-4298; S. Eichenseher, K. Kromm, O. Delacroix, J. A. Gladysz, Chem. Commun. 2002, 1046-1047). Tetrafluoroborates were selected, because this anion does not have a coordinating effect, and therefore has no adverse effect on the catalysis reaction. However, it was shown that trialkylphosphonium tetrafluoroborates have a strong corrosive effect. For example, tricyclohexyl phosphonium tetrafluoroborate has such a strong corrosive effect that a glazed porcelain bowl, in which the substance was dried, became matte due to the effect of the fluoride released from this substance. The use of this substance, for example, should therefore be avoided in enameled pans and glass lined vessels.
Also previously described are:                The preparation of trialkylphosphonium chlorides (K. L. Tan, S. Park, J. A. Ellman, R. G. Bergman, J. Org. Chem. 2004, 69, 7329-7335); these are very hygroscopic, and must be handled under inert gas.        The preparation of trialkylphosphonium tetraphenylborates (D. G. Gusev, R. Hübener, P. Burger, O. Orama, H. Berke, J. Am. Chem. Soc. 1997, 119, 3716-3731); however, tetraphenylborates as counterions are not available inexpensively.        Chiral diphosphine salts with at least one phospholane group (WO-A-2004/098772), as non-, or little hygroscopic and stable when exposed to air catalyst ligand precursors; the bismethanesulfonate of RoPHOS (1,2-bis[(2S,3S,4S,5S)-3,4-bis(benzyloxy)-2,5-dimethyl-phospholanyl]benzene) is very hygroscopic, and not stable when exposed to air.        The preparation of air stable bisphosphonium salts with sterogenic centers at the phosphor atoms, and trifluoromethane sulfonate as counterions from the borane adduct of phosphates (H. Danjo, W. Sasaki, T. Miyazaki, T. Imamoto, Tetrahedron Lett. 2003, 44, 3467-3469).        The 31P-NMR spectrum of a solution of tributylphosphonium trifluoromethane sulfonate in methylene chloride at −70° C. (P. Kubisa, S. Penczek, Makromol. Chem. 1979, 180, 1821-1823). The isolation of the salt is not described.        The protonation enthalpies of various phosphines with trifluoromethane sulfonic acid (R. J. Anelici, Acc. Chem. Res. 1995, 28, 51-60). The isolation of the salts is not described.        The enthalpy of formation of fluorinated trialkylphosphonium trifluoromethane sulfonates and their 31P-NMR spectra (H. Jiao, S. Le Stang, T. Soós, R. Meier, K. Kowski, P. Rademacher, L. Jafarpour, J.-B. Hamard, S. Nolan, J. A. Gladysz, J. Am. Chem. Soc. 2002, 124, 1516-1523 The isolation of the salts is not described.        The 1J(31P-1H) coupling constant of various phosphonium sulfonates prepared only as a solution in fluorosulfonic acid (F. Krech, A. Zschunke, Z. inorg. Chem. 1978, 440, 45-51).        A Heck reaction known in the literature with tricyclohexylphosphine or tri-tert-butylphosphine as the catalyst ligand (WO-A-02/085843; R. A. Singer, J. D. McKinley, G. Barbe, R. A. Farlow Org. Lett. 2004, 6, 2357-2360); express reference is made to the sensitivity to air of tricyclohexylphosphine: the phosphine should only be used from freshly opened vessels. This will hamper stock-piling, which requires that either containers must be filled with the required amount, or that residual amounts not to be used must be discarded.        WO-A-2004/098772 discloses the use of phospholane salts in enantioselective hydrogenation. Notably this document discloses the use of triflates and tetrafluoroborates of phospholanes as being non-hydroscopic while the mesylate is found to be very hygroscopic.        Thus the aim of the present invention is to provide phosphonium salts that overcome the disadvantages of the compounds described in prior art, in particular, they should not be corrosive, while at the same time remain non-, or only little hygroscopic.        